Various systems for arresting a vehicle are well known in the art and have been employed for many uses such as control of railroad grade crossings and police and construction roadway barriers. Such systems range from relatively rigid (i.e. fixed) physical barriers such as guard rails to relatively mobile (i.e. flexible) barriers such as beams or nets disposed across the roadway. Barriers proposed in Terio, U.S. Pat No. 4,576,507 and Waldecker, U.S. Pat No 4,824,282 illustrate systems configured to be disposed below-ground and rapidly raised as needed. Such systems employ various deceleration means such as deflation bags and nets connected to shock absorbing pistons. A vehicle striking the barrier will first impact the inflated bags and thereafter the net will be pushed forward in opposition to a yielding resistance of the shock absorbing pistons. Such systems are disadvantageous in they apply the same braking force regardless of vehicle weight or speed. The result is that a lighter vehicle is brought to an abrupt stop which may result in injury to the vehicle and its occupants.
With respect to prior art vehicle arresting systems, these systems are also disadvantageous in that they utilize components which are likely to degrade over time and make the system unreliable and costly to maintain. When stored under a roadway for long periods of time, deflation bags are susceptible to developing leaks. Likewise, energy dissipating pistons are typically either hydraulic in nature and require regular maintenance to insure proper fluid levels or employ springs which lose strength over time. Thus, a need exists for a suitable system for arresting vehicles with minimal injury to the vehicle or its occupants which requires little maintenance.